Module 6. Optics Unit 1. Concept of Light. Active vocabulary

1. (To) absorb [əb'zɔːb] поглинати

2. Accuracy ['ækjərəsɪ] точність, правильність

3. Collision [kə'lɪʒn] зіткнення

4. Diffraction [dɪ'frækʃ(ə)n] дифракція

5. Discrepancy [dɪs'krep(ə)nsɪ] розбіжність, суперечність, різниця

6. Distance ['dɪst(ə)ns] відстань

7. Dual nature ['djuːəl 'neɪʧə] подвійна природа

8. Eclipse [ɪ'klɪps] затемнення

9. Emission [ɪ'mɪʃ(ə)n] (of light) виділення/розповсюдження світла

10. (To) emit [ɪ'mɪt] виділяти, випромінювати

11. (To) estimate ['estɪmeɪt] оцінювати, підраховувати

12. Filament ['fɪləmənt] нитка розжарення

13. Finite speed ['faɪnaɪt spiːd] кінцева (обмежена) швидкість

14. Frequency ['friːkwənsɪ] частота

15. Instantaneously [ˌɪnstən'teɪnɪəslɪ] миттєво, моментально, негайно

16. Light beam [laɪt'biːm] (a beam of light) пучок світла, промінь світла

17. Light year ['laɪtˌjɪə] світловий рік

18. Mirror ['mɪrə] дзеркало

19. Moon [muːn] супутник (планети), Місяць

20. Octagonal [ɒk'tegən(ə)l] восьмикутний

21. Opaque [əu'peɪk] непрозорий, світлонепроникний

22. Particle ['pɑːtɪk(ə)l] частинка

23. Photon ['fəutɒn] фотон

24. (To) reflect [rɪ'flekt] відбивати

25. Reflection [rɪ'flekʃ(ə)n] відбиття

26. Semitransparent [ˌsemɪtræn'spærənt] напівпрозорий

27. Speed of light ['spiːd əv'laɪt] швидкість світла

28. (To) spread out ['spred aut] поширюватись, розповсюджувати

29. Springy ['sprɪŋɪ] (elastic) пружній, еластичний

30. Sta­tionary ['steɪʃən(ə)rɪ] нерухомий

31. Time delay ['taɪm dɪ'leɪ] затримка у часі

32. (To) transfer [træns'fɜː] переносити, переміщувати

33. Transparent [træns'pærənt] прозорий

34. Vibration [vaɪ'breɪʃ(ə)n] вібрація, коливання

35. Visible ['vɪzəb(ə)l] видимий

36. Vision ['vɪʒ(ə)n] видимість, зір, бачення

Pre-reading task (discussion)

Exercise 1. Read the definition of optics as a part of physics and discuss the questions below.

Optics is the branch of physics that studies the physical properties of light.

1. What question can optics answer?

2. What are the common sources of light?

3. How do we call the materials that allow light to pass through? What examples can you give?

4. How do we call the materials that block light and do not allow it to pass through? Give your examples.

Reading

Exercise 2. Read and translate the text below.

Pay attention to some proper names: Socrates ['sɒkrəˌtiːz] – Сократ, Plato['pleɪtəʊ] – Платон, Euclid ['juːklɪd] – Евклід, Empedocles [em'pedəˌkliːz] – Емпедокл, Christian Huygens ['krɪstʃən 'haɪgənz] – Христіа́н Гюйгенс, Einstein ['aɪnstaɪn] – Ейнштейн, Ole Roemer [ɔːlə 'ræmə] – Оле Ремер, Albert Michelson ['ælbət 'maɪkəlsən] – Альберт Майкельсон, Alpha Centauri ['ælfə'sentɔːri] – Альфа Центавра.

Early concepts of light

Light has been studied for thousands of years. Some of the ancient Greek philosophers thought that light consisted of tiny particles, which could enter the eye to create the sensation of vision. Others, including Socrates and Plato, thought that vision resulted from filaments emitted by the eye making contact with an object. This view was supported by Euclid, who explained why we do not see a needle on the floor until our eyes fall upon it. Up until the time of Newton and beyond, most philosophers and scientists thought that light consisted of particles. However, one Greek, Empedocles, taught that light traveled in waves. One of Newton’s contemporaries, the Dutch scientist Christian Huygens, also argued that light was a wave. The particle theory was supported by the fact that light seemed to move in straight lines instead of spreading out as waves do. Huygens provided evidence that under some circumstances light does spread out (diffraction). Other scientists later found more evidence to support the wave theory. The wave theory became the accepted theory in the nineteenth century. Then in 1905 Einstein published a theory explaining the photo­electric effect. According to this theory, light consists of particles called photons. Photons are massless bundles of concentrated electromag­netic energy. Scientists now agree that light has a dual nature, particle and wave.